Hypertension is a major problem in african-Americans but the factors contributing to this are poorly understood. This research proposal will compare vascular response and sympathetic regulation in African- Americans and Caucasians allow examination of both factors and their interaction. These studies will attempt to physiologically localize the site of the attenuated response to isoproterenol that we have demonstrated and focus future molecular biology, mechanism-based, techniques on these potential target sites. An understanding of the regulation of sympathetic activity by diurnal rythymn and stress will provide information about the role of these two mechanisms in the pathogenesi of hypertension and allow characterization of a prehypertensive state during which pharmacological intervention could arrest or retard the process.